I've run nothing but 87 octane since day one. No idea what the dealer pre-filled it with for me when I took delivery, although I'm willing to bet it wasn't high-test.
No issues running on 87. I have no doubt I'm down a few horsepower because of the lower octane and the engine auto-adjusting timing etc etc, but whatever power I have lost can't be a whole lot since this thing still goes like stink whenever I want it to. And for my purposes, which is basically commuting to and from work on the highway in a heavily trafficked multi-city area, I will never be racing it at 240kph or drag racing it on a regular basis, and if I ever want to tow with it or take it on a very hilly drive on a hot day I'll fill it with high test first.
Averaging just around 20-21 mpg consistently since day one.
Edit: Yes, now you may all go ahead and lambaste me for not using 93 octane. Go ahead, I'll wait lol.